Children as young as 10 are fare dodging and causing disorder at train stations, prompting a police crackdown in West Auckland.
Auckland Transport is also considering "gating" a further nine of its stations throughout its rail network.
Problems with fare dodgers, general disorder and young people accessing restricted areas such as train tracks have culminated in a number of incidents across the city in recent times, and are causing growing safety concerns from rail staff.
Henderson police started up Operation Derail in May as a response to trouble on and around trains, said acting Senior Sergeant Andy Burdett.
"We have been talking to members of the community and along with our own observations have identified a number of issues around train stations and into the CBDs of the West Auckland region."
He said there had been a number of arrests and many of the issues related to young people - some as young as 10 - who were catching trains into the main hubs and causing disorder.
"Youth on the trains, a lot are not paying and also there are a number who regularly trespass around the rail network. There have been a number of arrests and a number of missing people found through checking as they come off the trains.
"There have been quite a few cases in particular of very young kids found using the rail network to come into the CBD late at night, and they are getting taken home to their parents.
"There were also concerns for the safety of track inspectors and security staff," Mr Burdett said.
Operation Derail meant extra patrols had been running from 4pm to midnight on Thursday and Friday nights on train platforms since May.
Police were also working with AT and Transdev Auckland - the company that operates the passenger rail network - to improve security.
An AT spokesman said it was hoped a proposal to install gates at nine more stations would address the issues.
Britomart, Newmarket and Manukau stations are gated - where only people with valid tickets can enter and exit - with New Lynn set to join the list this month.
"Gating is being considered at a further nine stations subject to business cases and funding. The stations currently gated, including New Lynn, account for 79 per cent of all passenger trips.
"If we extended gating to another nine stations we would cover 98.48 per cent of passenger trips."
He said extra security had been added to cover 14 high-risk stations and Pacific wardens had been employed in addition to Maori wardens.